Methods for evaluating and improving drilling operations

ABSTRACT

A method for improving drilling performance of a drilling tool assembly is disclosed. The method includes identifying a drilling performance parameter to be improved. One or more potential solutions are defined to improve the drilling performance parameter. A drilling simulation is performed to determine the dynamic response of the drilling tool assembly during a drilling operation. Determining the dynamic response includes determining the interaction of a cutting element of a drill bit with an earth formation. Improvement in the drilling performance parameter is determined based upon the drilling simulation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Pat. No. 6,785,641,issued on Aug. 31, 2004, and claims the benefit, pursuant to 35 U.S.C.§120, of that patent. That patent is incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

FIG. 1 shows one example of a conventional drilling system for drillingan earth formation. The drilling system includes a drilling rig 10 usedto turn a drilling tool assembly 12 that extends downward into a wellbore 14. The drilling tool assembly 12 includes a drilling string 16,and a bottomhole assembly (BHA) 18, which is attached to the distal endof the drill string 16. The “distal end” of the drill string is the endfurthest from the drilling rig.

The drill string 16 includes several joints of drill pipe 16 a connectedend to end through tool joints 16 b. The drill string 16 is used totransmit drilling fluid (through its hollow core) and to transmitrotational power from the drill rig 10 to the BHA 18. In some cases thedrill string 16 further includes additional components such as subs, pupjoints, etc.

The BHA 18 includes at least a drill bit 20. Typical BHA's may alsoinclude additional components attached between the drill string 16 andthe drill bit 20. Examples of additional BHA components include drillcollars, stabilizers, measurement-while-drilling (MWD) tools,logging-while-drilling (LWD) tools, subs, hole enlargement devices(e.g., hole openers and reamers), jars, accelerators, thrusters,downhole motors, and rotary steerable systems.

In general, drilling tool assemblies 12 may include other drillingcomponents and accessories, such as special valves, such as kelly cocks,blowout preventers, and safety valves. Additional components included ina drilling tool assembly 12 may be considered a part of the drill string16 or a part of the BHA 18 depending on their locations in the drillingtool assembly 12.

The drill bit 20 in the BHA 18 may be any type of drill bit suitable fordrilling earth formation. Two common types of drill bits used fordrilling earth formations are fixed-cutter (or fixed-head) bits androller cone bits. FIG. 2 shows one example of a fixed-cutter bit. FIG. 3shows one example of a roller cone bit.

Referring to FIG. 2, fixed-cutter bits (also called drag bits) 21typically comprise a bit body 22 having a threaded connection at one end24 and a cutting head 26 formed at the other end. The head 26 of thefixed-cutter bit 21 typically includes a plurality of ribs or blades 28arranged about the rotational axis of the drill bit and extendingradially outward from the bit body 22. Cutting elements 29 are embeddedin the raised ribs 28 to cut formation as the drill bit is rotated on abottom surface of a well bore. Cutting elements 29 of fixed-cutter bitstypically comprise polycrystalline diamond compacts (PDC) or speciallymanufactured diamond cutters. These drill bits are also referred to asPDC bits.

Referring to FIG. 3, roller cone bits 30 typically comprise a bit body32 having a threaded connection at one end 34 and one or more legs(typically three) extending from the other end. A roller cone 36 ismounted on each leg and is able to rotate with respect to the bit body32. On each cone 36 of the drill bit 30 are a plurality of cuttingelements 38, typically arranged in rows about the surface of the cone 36to contact and cut through formation encountered by the drill bit.Roller cone bits 30 are designed such that as a drill bit rotates, thecones 36 of the roller cone bit 30 roll on the bottom surface of thewell bore (called the “bottomhole”) and the cutting elements 38 scrapeand crush the formation beneath them. In some cases, the cuttingelements 38 on the roller cone bit 30 comprise milled steel teeth formedon the surface of the cones 36. In other cases, the cutting elements 38comprise inserts embedded in the cones. Typically, these inserts aretungsten carbide inserts or polycrystalline diamond compacts. In somecases hardfacing is applied to the surface of the cutting elementsand/or cones to improve wear resistance of the cutting structure.

For a drill bit 20 to drill through formation, sufficient rotationalmoment and axial force must be applied to the drill bit 20 to cause thecutting elements of the drill bit 20 to cut into and/or crush formationas the drill bit is rotated. The axial force applied on the drill bit 20is typically referred to as the “weight on bit” (WOB). The rotationalmoment applied to the drilling tool assembly 12 at the drill rig 10(usually by a rotary table or a top drive mechanism) to turn thedrilling tool assembly 12 is referred to as the “rotary torque”. Thespeed at which the rotary table rotates the drilling tool assembly 12,.typically measured in revolutions per minute (RPM), is referred to asthe “rotary speed”. Additionally, the portion of the weight of thedrilling tool assembly supported at the rig 10 by the suspendingmechanism (or hook) is typically referred to as the hook load.

During drilling, the actual WOB is not constant. Some of the fluctuationin the force applied to the drill bit may be the result of the drill bitcontacting with formation having harder and softer portions that breakunevenly. However, in most cases, the majority of the fluctuation in theWOB can be attributed to drilling tool assembly vibrations. Drillingtool assemblies can extend more than a mile in length while being lessthan a foot in diameter. As a result, these assemblies are relativelyflexible along their length and may vibrate when driven rotationally bythe rotary table. Drilling tool assembly vibrations may also result fromvibration of the drill bit during drilling. Several modes of vibrationare possible for drilling tool assemblies. In general, drilling toolassemblies may experience torsional, axial, and lateral vibrations.Although partial damping of vibration may result due to viscosity ofdrilling fluid, friction of the drill pipe rubbing against the wall ofthe well bore, energy absorbed in drilling the formation, and drillingtool assembly impacting with well bore wall, these sources of dampingare typically not enough to suppress vibrations completely.

Vibrations of a drilling tool assembly are difficult to predict becausedifferent forces may combine to produce the various modes of vibration,and models for simulating the response of an entire drilling toolassembly including a drill bit interacting with formation in a drillingenvironment have not been available. Drilling tool assembly vibrationsare generally undesirable, not only because they are difficult topredict, but also because the vibrations can significantly affect theinstantaneous force applied on the drill bit. This can result in thedrill bit not operating as expected. For example, vibrations can resultin off-centered drilling, slower rates of penetration, excessive wear ofthe cutting elements, or premature failure of the cutting elements andthe drill bit. Lateral vibration of the drilling tool assembly may be aresult of radial force imbalances, mass imbalance, and drillbit/formation interaction, among other things. Lateral vibration resultsin poor drilling tool assembly performance, overgage hole drilling,out-of-round, or “lobed” well bores and premature failure of both thecutting elements and drill bit bearings.

When the drill bit wears out or breaks during drilling, the entiredrilling tool assembly must be lifted out of the well boresection-by-section and disassembled in an operation called a “pipetrip”. In this operation, a heavy hoist is required to pull the drillingtool assembly out of the well bore in stages so that each stand of pipe(typically pipe sections of about 90 feet) can be unscrewed and rackedfor the later re-assembly. Because the length of a drilling toolassembly may extend for more than a mile, pipe trips can take severalhours and can pose a significant expense to the well bore operator anddrilling budget. Therefore, the ability to design drilling toolassemblies which have increased durability and longevity, for example,by minimizing the wear on the drilling tool assembly due to vibrations,is very important and greatly desired to minimize pipe trips out of thewell bore and to more accurately predict the resulting geometry of thewell bore drilled.

Many companies offer drilling services for the purposes of improvingdrilling performance. These services typically include modeling up toaround 200 feet of the BHA with representative factors assumed for theinfluence of the drill string and the drill bit during drilling. Thedrill string is typically modeled as a spring and the spring constantassumed based on the expected configuration of the drill string. The BHAis typically modeled as a beam suspended from the spring at one end andexcited by an excitation at the other end assumed to represent theexcitation resulting from a drill bit interacting with the formation.

While prior art simulation methods, such as those described aboveprovide a general means for predicting drilling tool assembly dynamics,simulation techniques have not been developed to cover actual drillingwith a drilling tool assembly in a well bore including a completesimulation of the drill string, the BHA, and the drill bit that takesinto account the interaction of the cutting elements on the drill bitwith the earth formation being drilled. As a result, accurately modelingand predicting the response of a drilling tool assembly during drillinghas been virtually impossible. Additionally, the change in the dynamicresponse of a drilling tool assembly while drilling when a component ofthe drilling tool assembly is changed has not been well understood.

Prior art drill bit simulation methods have been developed and used forthe design or selection of drill bits independent of the drilling toolassemblies with which the drill bits will be used. As a result,optimized drill bit selection and design is typically an iterativeprocess, which requires the collection and evaluation of fieldperformance data obtained from many field runs using a selected drillbit. When a trend of drilling problems is found to occur for aparticular bit, such as low rate of penetration or premature drill bitfailure, a new drill bit may be selected or an adjustment made to thecurrent bit design in hopes of obtaining better drilling performance infuture runs. A design change or selection of a new drill bit is madeindependent of the drilling tool assembly with which the drill bit willbe used, and many field runs with the new bit may occur before theactual drilling performance of the new drill bit can be confirmed.Similar iterative methods are used to determine an optimum or preferredselection of components in a drilling tool assembly. Such iterativedesign and selection methods are time consuming and can be costly fordrilling operations. In particular, replacement of a poorly performingdrill bit or failure of another component of a drilling tool assemblyrequires the time and expense of removing the drilling tool assemblyfrom the well bore, which may take many hours depending on the depth ofthe well. Also, in many cases, after using several different drill bitdesigns in an attempt to improve drilling performance in a series ofwells, it may later be determined that drilling problems may have beenbetter corrected by changing other parameters of the drilling toolassembly, such as operating parameters for drilling or the make up ofthe BHA to avoid or minimize vibration modes of the drilling toolassembly during drilling.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a method for improvingdrilling performance of a drilling tool assembly. The method includesidentifying a drilling performance parameter to be improved. At leastone potential solution is defined to improve the drilling performanceparameter. Next, a drilling simulation of the at least one potentialsolution is performed. The drilling simulation includes simulating aneffect on the drilling tool assembly of an interaction of a cuttingelement of a drill bit with an earth formation. Improvement in thedrilling performance parameter is determined based upon the drillingsimulation.

In another aspect, the present invention relates to a drilling toolassembly designed using the above method.

In one aspect, the present invention relates to a computer system forimproving drilling performance of a drilling tool assembly. The computersystem includes a processor, a memory, a storage device, and softwareinstructions stored in the memory. The software instruction enable thecomputer system under control of the processor to identify a drillingperformance parameter to be improved, define at least one potentialsolution to improve the drilling performance parameter, and perform adrilling simulation of the at least one potential solution. The drillingsimulation includes simulating an effect on the drilling tool assemblyof an interaction of a cutting element of a drill bit with an earthformation. Further, the software instructions determine, based upon thedrilling simulation, whether the drilling performance parameter isimproved by the at least one potential solution.

In one aspect, the present invention relates to a method for improvingdrilling performance of a drilling tool assembly. The method includesperforming a drilling simulation to simulate an original drillingoperation. The drilling simulation includes simulating an effect on thedrilling tool assembly of an interaction of a cutting element of a drillbit with an earth formation. A solution to improve a drillingperformance parameter is defined based upon the drilling simulation.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a prior art drilling system fordrilling earth formations.

FIG. 2 shows a perspective view of a prior art fixed-cutter bit.

FIG. 3 shows a perspective view of a prior art roller cone bit.

FIG. 4 shows a flow chart of a method in accordance with one embodimentof the present invention.

FIG. 5 shows an input screen for a drilling simulation in accordancewith one embodiment of the present invention.

FIG. 6 shows an input screen for a drilling simulation in accordancewith one embodiment of the present invention.

FIG. 7A shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 7B shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 8 shows a graphical visualization of a drilling tool assembly inaccordance with one embodiment of the present invention.

FIG. 9A shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 9B shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 10A shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 10B shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 11 shows a graphical visualization of a drilling tool assembly inaccordance with one embodiment of the present invention.

FIG. 12A shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 12B shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 13A shows an input screen for a drilling simulation in accordancewith one embodiment of the present invention.

FIG. 13B shows a graphical visualization of a well bore in accordancewith one embodiment of the present invention.

FIG. 14 shows an input screen for a drilling simulation in accordancewith one embodiment of the present invention.

FIG. 15 shows a tabular output of a drilling simulation in accordancewith one embodiment of the present invention.

FIG. 16 shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 17A shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 17B shows a graphical visualization of a drilling performanceparameter from a drilling simulation in accordance with one embodimentof the present invention.

FIG. 18 shows a computer system in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION

In one aspect, the present invention provides a method for evaluatingdrilling information to provide a solution to improve drillingperformance. In one embodiment, the method includes obtaining drillinginformation and evaluating the drilling information to determine theperformance of an actual drilling tool assembly in drilling earthformation or to establish the expected performance of a proposeddrilling tool assembly in drilling earth formation. The method mayfurther include utilizing the evaluation and/or the determinedperformance of the drilling tool assembly to define at least onepotential solution to improve the drilling performance of the actual orproposed drilling tool assembly. A solution may involve any combinationof adjustments to the drilling tool assembly design parameters or theoperating parameters used for drilling with the drilling tool assembly.

In another aspect, the present invention provides a method for improvingthe drilling performance of a drilling tool assembly. In one embodiment,the method includes obtaining and evaluating drilling information toidentify potential solutions to improve drilling performance. The methodfurther includes performing dynamic simulation for the potentialsolutions and comparing simulation results for the at least onepotential solutions to at least one selected drilling performancecriterion. Then, based on the comparison, selecting at least onesolution for use in drilling a well bore.

In selected embodiments, the method may further include using theselected solution in the drilling of a well bore and obtaining post-rundrilling information from the well drilled using the solution. Thepost-run drilling information may be compared to drilling simulationresults and/or the at least one selected drilling performance criterionto determine if further improvement in drilling performance is desired.If further improvement is desired, the post-run drilling information maybe evaluated and used to identify new potential solutions to furtherimprove drilling performance. The post-run drilling information may alsobe used to recalibrate the simulation system to more closely match theactual drilling operation.

Drilling performance may be measured by one or more drilling performanceparameters. Examples of drilling performance parameters include rate ofpenetration (ROP), rotary torque required to turn the drilling toolassembly, rotary speed at which the drilling tool assembly is turned,drilling tool assembly lateral, axial, or torsional vibrations inducedduring drilling, weight on bit (WOB), forces acting on components of thedrilling tool assembly, and forces acting on the drill bit andcomponents of the drill bit (e.g., on blades, cones, and/or cuttingelements). Drilling performance parameters may also include theinclination angle and azimuth direction of the borehole being drilled.One skilled in the art will appreciate that other drilling performanceparameters exist and may be considered without departing from the scopeof the invention.

In accordance with one or more embodiments of the invention, a drillingtool assembly includes at least one segment (or joint) of drill pipe anda drill bit. The components of a drilling tool assembly may be moregenerally referred to as a drill string and a bottomhole assembly (BHA).The drill string as discussed herein refers to a string of drill pipe,which includes one or more joints of drill pipe. The BHA includes atleast a drill bit.

In a typical drilling tool assembly, the drill string includes severaljoints of drill pipe connected end to end, and the bottomhole assemblyincludes one or more drill collars and a drill bit attached to an end ofthe BHA. The BHA may further include additional components, such asstabilizers, a downhole motor, MWD tools, and LWD tools, subs, holeenlargement devices, jars, accelerators, thrusters, and/or a rotarysteerable system, for example. Therefore, in accordance with embodimentsof the invention, a drilling tool assembly may be a single segment ofdrill pipe attached to a drill bit, or as complex as a multi-componentdrill string that includes a kelly, a lower kelly cock, a kelly saversub, several joints of drill pipe with tool joints, etc., and amulti-component BHA that includes drill collars, stabilizers, and otheradditional specialty items (e.g., reamers, valves, MWD tools, mudmotors, rotary steerable systems, etc.) and a drill bit.

While the BHA is generally considered to include a drill bit, in theexample drilling simulation method discussed below, the detailedinteraction of the drill bit with the bottomhole surface during drillingis generally considered separately. This separate consideration of thedrill bit in detail allows for the interchangeable use of any drill bitmodel in the drilling tool assembly simulation as determined by thesystem designer. Drill bits used and modeled in one or more embodimentsof the invention may include, for example, fixed cutter bits, rollercone bits, hybrid bits (bits having a combination of fixed cutters androlling cutting structure), bi-centered bits, reaming bits, or any othercutting tool used during the drilling of earth formation. One ofordinary skill in the art will appreciate that the drilling simulationmethod may consider the drill bit jointly with the drilling toolassembly without departing from the scope of the invention.

One example of a method that may be used to simulate a drilling toolassembly in accordance with one or more embodiments of the invention isdisclosed in U.S. patent application Ser. No. 09/689,299 entitled“Simulating the Dynamic Response of a Drilling Tool Assembly and itsApplication to Drilling Tool Assembly Design Optimizing and DrillingPerformance Optimization”, which has been incorporated by reference inits entirety. In accordance with this method, properties of the drillingto be simulated are provided as input. The input may include drillingtool assembly design parameters, well bore parameters, and drillingoperating parameters.

Examples of drilling tool assembly design parameters include the type,location, and number of components included in the drilling toolassembly; the length, ID, OD, weight, and material properties of eachcomponent; the type, size, weight, configuration, and materialproperties of the drill bit; and the type, size, number, location,orientation, and material properties of the cutting elements on thedrill bit. Material properties in designing a drilling tool assembly mayinclude, for example, the strength, elasticity, and density of thematerial. It should be understood that drilling tool assembly designparameters may include any other configuration or material parameter ofthe drilling tool assembly without departing from the scope of theinvention.

The geometry and material properties (“bit design parameters”) of thedrill bit are typically defined in greater detail than other componentsin the drilling tool assembly. Examples of simulation methods for drillbits are provided in U.S. Pat. No. 6,516,293, entitled “Method forSimulating Drilling of Roller Cone Bits and its Application to RollerCone Bit Design and Performance,” and U.S. Provisional Application No.60/485,642, filed Jul. 9, 2003 and entitled “Methods for Modeling,Designing, and Optimizing Fixed Cutter Bits,” which are both assigned tothe assignee of the present invention and now incorporated herein byreference in their entirety. In accordance with this method, the bitdesign parameters include the cutting structures on the drill bit, suchas cutting element geometry, quantity, and locations. As with othercomponent in the drilling tool assembly, the material properties of thedrill bit are defined. In one embodiment, the drill bit is defined withthe drilling tool assembly. In another embodiment, the drill bit may bedefined separately and stored in a library of drill bit designs. Theseparate drill bit could then be selected and integrated with thedrilling tool assembly. In another embodiment, other components in thedrilling tool assembly may also be defined separately and stored in alibrary. The library approach reduces the need to redefine componentsunnecessarily.

Well bore parameters typically include the geometry of a well bore andformation material properties. The trajectory of a well bore in whichthe drilling tool assembly is to be confined also is defined along withan initial well bore bottom surface geometry. Because the well boretrajectory may be straight, curved, or a combination of straight andcurved sections, well bore trajectories, in general, may be defined bydefining parameters for each segment of the trajectory. For example, awell bore may be defined as comprising N segments characterized by thelength, diameter, inclination angle, and azimuth direction of eachsegment and an indication of the order of the segments (i.e., first,second, etc.). Well bore parameters defined in this manner can then beused to mathematically produce a model of the entire well boretrajectory. Formation material properties at various depths along thewell bore may also be defined and used. One of ordinary skill in the artwill appreciate that well bore parameters may include additionalproperties, such as friction of the walls of the well bore and well borefluid properties, without departing from the scope of the invention.

Drilling operating parameters typically include the rotary table (or topdrive mechanism), speed at which the drilling tool assembly is rotated(RPM), the downhole motor speed (if a downhole motor is included) andthe hook load. Drilling operating parameters may further includedrilling fluid parameters, such as the viscosity and density of thedrilling fluid, for example. It should be understood that drillingoperating parameters are not limited to these variables. In otherembodiments, drilling operating parameters may include other variables,e.g. rotary torque and drilling fluid flow rate. Additionally, drillingoperating parameters for the purpose of drilling simulation may furtherinclude the total number of drill bit revolutions to be simulated or thetotal drilling time desired for drilling simulation. Once the parametersof the system (drilling tool assembly under drilling conditions) aredefined, they can be used along with various interaction models tosimulate the dynamic response of the drilling tool assembly drillingearth formation as described below.

FIG. 4 shows one embodiment of a method that involves the evaluating ofdrilling information to provide a solution to improve a drillingperformance. The method includes obtaining drilling information (step510). Drilling information may include information characterizing thegeometry of a well bore, geological information, a drilling toolassembly design, and drilling operating parameters. The drillinginformation may be obtained from offset wells, which are existing wellsclose to the proposed location of a planned well. An offset welltypically provides formation properties that are very similar to whatwill be encountered when drilling another nearby well. In someinstances, the offset wells may be those previously drilled by adriller, and that driller may want to improve drilling operationsconducted for similar future wells. Alternatively, the drillinginformation may be provided from a proposed well plan created by acustomer, such as a drilling operator, directional company, or drillingcontractor, with the desired geometry for the well defined by thecustomer and the geological information, such as formation type and rockstrength, obtained from offset well data. For example, formation typemay be obtained from mud logs, and rock strength may be calculated fromsonic, density and/or porosity logs for wells in the area. The drillingtool assembly design and drilling operating parameters may be providedby the customer. In some cases, a drilling tool assembly design anddrilling operating parameters may be created by a designer based onother drilling information. One of ordinary skill in the art willappreciate that more or less drilling information may be provided fromdifferent sources or selected without departing from the scope of thepresent invention.

The drilling information obtained from step 510 is then evaluated toidentify at least one potential solution that may be applied to adrilling operation to improve drilling performance (step 520). Theevaluation of drilling information may be performed in various ways. Insome embodiments, the experience of a drilling engineer (or a drillingtool assembly design engineer) may be used to evaluate the drillinginformation and define potential solutions to improve drillingperformance. In other embodiments, a neural network on a computer maygenerate solutions based on an evaluation of the drilling informationand past experience. In one or more embodiments, a drilling engineer mayperform a drilling simulation based on the drilling information toconfirm that a simulation will give a good representation of actualdrilling and/or to identify potential causes of reduced drillingperformance. One of ordinary skill in the art will appreciate that theevaluation of drilling information to identify or define potentialsolutions to improve drilling performance may be performed in a numberof different ways without departing from the scope of the presentinvention.

Next, drilling with each of the potential solutions is simulated (step530). Specifically, the drilling simulations include drilling through anearth formation with a selected drilling tool assembly wherein theeffects on the drilling tool assembly caused by the interaction of oneor more cutting elements on the drill bit with the earth formation isdetermined. The simulation takes into account the dynamic response ofthe drilling tool assembly in drilling through the earth formation underthe defined drilling operation parameters. The interaction between theselected drill bit and the earth formation is calculated and its effecton the drilling tool assembly determined.

The drilling simulations for the potential solutions are compared to aselected drilling performance criterion, and based on the comparison, atleast one of the potential solutions is selected (step 540) as asolution to improve drilling performance. This may be done by comparingthe recorded results for each potential solution to each other in viewof a selected drilling performance criterion, such as a desire for amaximum ROP, wherein the potential solution resulting in a simulatedresponse that best satisfies the selected drilling performance criterionis selected and proposed as the solution for improving drillingperformance. Typically, at least one drilling performance criterion isselected from drilling performance parameters and used as a metric forthe solutions defined from the analysis of drilling information. Thedrilling performance criterion may relate to a selected ROP, drill bitlife, vibrations experienced by one or more components, predicted costof the well, WOB, forces on one or more components, or any other valueor parameter considered important in a particular drilling operationthat is desired to be improved. In some embodiments, more than onedrilling performance criterion may be used. One of ordinary skill in theart will appreciate that any relevant metric may be used to evaluatedrilling performance without departing from the scope of the invention.After selecting a solution (step 540), the selected solution can then beapplied to a drilling operation and used in the drilling of a well (step550)

Continuing with the method in FIG. 4, in one or more embodiments,further improvement or adjustment to the drilling performance may bedesired after using the solution in the drilling of a well (step 560).For example, to determine the effectiveness of a selected solutionapplied to a drilling operation, post-run drilling information may beobtained from the drilling performed with the provided solution (step570). The post-run information may be compared with a new or theoriginal selected drilling performance criterion (step 580). If furtherimprovement to the drilling performance is desired, the post-rundrilling information may be evaluated to define additional solutionsthat may improve drilling performance (step 520). This iterative processof obtaining post-run drilling information and evaluating it to defineadditional solutions may be repeated to further improve drillingperformance with each use of a solution to drill a well. In oneembodiment, the post-run drilling information may be compared to thedrilling simulation to calibrate the model.

In one embodiment, drilling information may be obtained from an offsetwell previously drilled by a customer. The drilling information mayinclude the desired well geometry and geological characteristics.Additionally, a previously used drilling assembly and drilling operatingparameters may also be provided by the customer. This drillinginformation may then be evaluated to define potential solutions. In oneembodiment, an engineer may model the drilling tool assembly used toobtain the drilling information and simulate drilling with it in thedefined drilling environment under the defined operation parameters toprovide a baseline for comparing potential solutions. This may also bedone to confirm the accuracy of the simulation model in predictingactual drilling responses and/or to identify the potential causes ofproblems that occurred during drilling. When preparing this baseline,potential solutions that may be applied to improve the drillingperformance may be observed without requiring further drillingsimulations. In another embodiment, an engineer or neural network mayevaluate the drilling information and define potential solutions basedon experience without requiring a baseline and, then, simulations may berun for the potential solutions.

In some embodiments, the drilling simulation provides several visualoutputs of the drilling performance parameters. The outputs may includetabular data of one or more drilling performance parameters.Additionally, the outputs may be in the form of graphs of a drillingperformance parameter, possibly with respect to time. A graphicalvisualization of drill string may also be output. The graphicalvisualization (e.g., 2-D, 3-D, or 4-D) may include a color scheme forthe drill string and BHA to indicate drilling performance parameters atlocations along the length of the drill string and bottom hole assembly.

The overall drilling performance of the drill string and bottom holeassembly may be determined by examining one or more of the availableoutputs. One or more of the outputs may be compared to the selecteddrilling performance criterion to determine suitability of a potentialsolution. For example, a 3-D graphical visualization of the drill stringmay have a color scheme indicating vibration quantified by the suddenchanges in bending moments through the drilling tool assembly. Timebased plots of accelerations, component forces, and displacements mayalso be used to study the occurrence of vibrations. Other drillingperformance parameters may also be illustrated simultaneously orseparately in the 3-D graphical visualization. Additionally, the 3-Dgraphical visualization may display the simulated drilling performed bythe drilling tool assembly.

For the purposes of illustration, a specific example in accordance withone embodiment of the present invention will now be described. In thishypothetical situation, a drilling operator has a plan to drill 10 wellsin one area of South Texas. During the drilling of the first well, thedrilling operator experienced low ROP and short drill bit life whiledrilling from 5,000 feet to 8,000 feet. The drilling operator wants toimprove drilling performance for the remaining wells. In accordance withone embodiment of the invention, an engineer obtains the drillinginformation from the previous well. The drilling information includesthe drilling tool assembly parameters, drilling operating parameters,and well parameters. Because the future wells will be drilled close tothe first well, the formation characteristics will be similar.Understanding the poor past drilling performance will allow forimprovements in drilling performance in the future wells.

First, the drilling operator provides a drilling engineer with drillinginformation, which includes the above information. In addition to thepreviously discussed information, pictures of the used drill bits areprovided. The wear patterns and dullness on the used drill bit suggestthat downhole vibrations are occurring locally at the drill bit. Thesevibrations were not detected by the surface sensors during drilling.This may be because vibrations were dampened before they reach thesurface or sensors positioned on the drilling tool assembly. Thissuggests that the vibrations may have been caused by the BHAconfiguration or the particular drill bit that was used. To evaluate thedrill bit as a potential cause, several drill bits are proposed as asolution to the drilling performance problems. The potential solutionsare to be compared based on ROP and lowest vibrations. A reduction invibrations is expected to increase the life of the drill bit. The nextstep is to simulate drilling with the candidate drill bits.

Next, the drilling tool assembly that was used for the first well ismodeled. FIG. 5 shows an example input screen used to define componentsof the drilling tool assembly in accordance with one embodiment of theinvention. In FIG. 5, a stabilizer is described by entering dimensionsand material properties into the input boxes 501. The component display502 shows the component that has been described. Other components arealso defined. The components are combined to form the drilling toolassembly. In this program, the components in the drilling tool assemblyare shown as a component list 503 and as a drilling tool assembly layout504. The drilling tool assembly will be kept the same between thesimulations, except for changing the drill bits.

Before the drilling simulation, the well bore environment is alsodefined. Well logs from the offset well previously drilled by thedrilling operator are used to model the well bore for simulationpurposes. Well bore parameters are entered into an input screen shown inFIG. 6 in accordance with one embodiment of the invention. The geometryof the well bore is entered into 510 in increments of depth. Theparticular well being simulated is 7,000 feet in total measured depth.Until 4,000 feet, the well is near vertical.

At this point, a build angle of 5 degrees per hundred feet begins untilreaching 65 degrees inclination at 5,300 feet total measured depth. Thewell is nearly straight beyond 5,300 feet. The drilling simulation willoccur at 7,000 feet while drilling mudstone having an unconfinedcompressive strength of 11,000 pounds per square inch.

Other well bore parameters are also entered into the input screen shownin FIG. 6. In this embodiment, the diameter, drilling fluid (mud)density, well stiffness, coefficient of restitution, and coefficients offriction are entered under well bore data 511. Well stiffness 522 ismeasured in pressure and refers to the mechanical strength of the wallof the well bore. The coefficient of restitution 517 refers to how muchenergy is dissipated or absorbed by the wall of the well bore when thedrilling tool assembly touches or impacts it. The coefficients offriction shown in FIG. 6 are transverse dynamic 518, transverse static519, axial dynamic 520, and axial static 521. The axial coefficients offriction refer to the friction experienced against the wall of the wellbore as the drilling tool assembly moves with the axis of the well bore.The transverse coefficients of friction refer to the frictionexperienced against the wall of the well bore as the drilling toolassembly moves perpendicular to the axis or rotates. The defined wellbore is shown in a tabular form 512, and may be viewed in athree-dimensional view 513.

After setting up the parameters for the drilling simulation, drillingwith each drill bit is simulated using the same drilling tool assemblyand in the same well bore. In this embodiment, the drilling operatingparameters are selected as appropriate for the designs of the candidatedrill bits. The drilling simulation includes the interaction of thecutting elements on the drill bit with the earth formation.

In this example, highest ROP and lowest vibrations are the selecteddrilling performance criteria. Upon completion of the drillingsimulations, the outputs of the simulations are compared to the selecteddrilling performance criteria. Various outputs are provided from thedrilling simulation to evaluate the drilling performance. Althoughadditional drilling simulations may be run, only two of the potentialsolutions are shown for clarity. The two solutions examined in greaterdetail are candidate drill bits A and B. FIGS. 7A and 7B are outputs ofthe drilling simulations in accordance with an embodiment of theinvention. Candidate drill bit B shown in FIG. 7B achieves a ROP of 90feet/hour, which is much greater than the 36 feet/hour achieved bycandidate drill bit A shown in FIG. 7A.

The other selected criterion is vibration of the drill bit, whichinfluences the life span of the drill bit. FIG. 8 shows athree-dimensional graphical representation of candidate drill bit A inaccordance with one embodiment of the invention. Instability of thedrill bit is indicated at 540 by a large bending moment. The experiencedbending moment is quantified by a scale 541. The instability isconfirmed by FIG. 9A, which displays the lateral vibration of candidatedrill bit A. The lateral vibration is measured in inch/second². The spanof large positive and negative acceleration indicates that the lateralvibration is problematic for candidate drill bit A. FIG. 9B displays thelateral vibration of candidate drill bit B, which is significantly lowerthan candidate drill bit B. FIGS. 10A and 10B display the axialvibrations experienced by candidate drill bits A and B, respectively.Candidate drill bit B experiences less axial vibrations than candidatedrill bit A.

In the example above, candidate drill bit B satisfied the drillingperformance criteria of high ROP and low vibrations. The use ofcandidate drill bit B is the selected solution for use in drilling thenext well by the drilling operator. The preceding example is only forthe purpose of illustrating the usage of a method in accordance with oneembodiment of the present invention. One of ordinary skill in the artwill appreciate that more or less drilling information can be obtainedfrom different sources without departing from the scope of theinvention. Additionally, other drilling performance criterion may beselected for improvement. The displays shown in the preceding exampleare not intended to limit the scope of the invention.

Another example of a method for evaluating drilling information toprovide a solution to improve drilling performance follows.Specifically, in this hypothetical, a customer has damaged an MWD toolwhile drilling a well offshore. The cause of the damage is unknown. Thedamage to the MWD tool has resulted in additional time and expense totrip the drilling tool assembly out of the well and replace the MWDtool. Additionally, repairing the MWD tool is costly. The customerwishes to discover the cause for the MWD damage and to have a solutionto prevent the damage to another MWD tool. To discover the cause,drilling information is obtained from the customer. To evaluate thedrilling information, the drilling tool assembly is modeled andsimulated as described with the drilling information. This drillingsimulation provides a baseline to understand the cause of the MWD damageand to define a solution to the problem.

Continuing with the MWD tool example, graphical outputs of drillingperformance characteristics from the drilling simulation are used toreveal the cause of the MWD damage. FIG. 11 is an example of a 3-Dgraphical representation of bending moments in a simulated drill stringand bottom hole assembly. In this example, the drill bit is a PDC drillbit 804 having 8 blades. The MWD tool location 801 is a few feet abovethe PDC drill bit 804. As shown, the scale 803 quantifies the bendingmoments throughout the model. Severe bending occurs at the MWD toollocation 801. However, the 3-D representation clearly shows that aminimal amount of bending occurs between the two stabilizers 802,indicating a suitable location for the MWD tool.

Vibration is examined at the MWD tool location 801 and at the suggestedlocation 901. FIGS. 12A and 12B display the vibrations experienced atthose locations, respectively. The comparison of the two locationsclearly indicates that relocating the MWD tool can prevent damage. Aproposed solution is to move the MWD tool to the suggested location 901between the two stabilizers 802. This solution does not require acomplete drilling simulation (including evaluating multiple solutions)because the initial drilling simulation during the evaluation clearlydefines the solution as moving the MWD tool between the stabilizers.

In some instances, the MWD tool must be located near the drill bit fordata gathering purposes. If moving the MWD tool to the suggestedlocation 901 is not acceptable, then other solutions to reduce vibrationof the MWD tool and optimize overall drilling performance may beproposed based on the drilling simulations of multiple alternativesolutions. For example, a different drill bit may be proposed, or astabilizer could be located closer to the drill bit. Many potentialsolutions may be available to reach a desired drilling performancelevel. The chosen solution will vary depending on the exact scenario.After defining potential solutions, the potential solutions may besimulated and selected as discussed in previous embodiments.

In some embodiments, a method for evaluating drilling information toimprove drilling performance is used to predict the direction ofdrilling and adjustments are made to the proposed drilling tool assemblyto obtain a desired well trajectory. Drilling simulation of a drillingtool assembly may assist in predicting the direction of drilling. Insome instances, the driller may require that directional motors be usedto “build” an angle in the well. A build angle is the rate that thedirection of the longitudinal axis of the well bore changes, which iscommonly measured in degrees per 100 feet. The extent of the build anglemay also be referred to as the “dogleg severity.” Another importantdirectional aspect is the “walk” rate. The walk rate refers to thechange in azimuthal (compass) direction of the well bore. Control andprediction of the drilling direction is important for reaching targetzones containing hydrocarbons.

In other cases, a driller might desire that the direction of the wellbore be maintained for a certain distance. One scenario is when adriller experiences difficulty in maintaining a vertical well bore whiledrilling through a particular rock formation. In this scenario, aportion of the well has already been drilled, and the well geometry canbe modeled to match the previously drilled well bore. To simulate thespecific rock, geological properties may be provided with the drillinginformation. The compressive rock strength and formation anisotropyindex (i.e., the variation of physical properties by direction in theformation) may be calculated from data from nearby wells or from thecurrent well bore.

Another example of a method for evaluating drilling information toprovide a solution to improve drilling performance follows.Specifically, in this hypothetical situation, a drilling operator inArgentina has experienced problems maintaining a vertical well duringdrilling. The rock hardness of the formation in the area requires a highWOB to drill efficiently with the drilling tool assembly used by thedrilling operator. It is also known that the formation dips at a 25degree angle, which contributes to the difficulty in maintaining avertical well. Starting at 2,500 feet, the drilling operator wants todrill a 16 inch diameter section to 5,000 feet while maintaining aninclination of less than 5 degrees

The first step is to obtain drilling information from an offset well.The WOB used previously is 80,000 lbs. The rock strength is 20,000pounds per square inch. The formation geometry is defined to have a dipangle of 25 degrees and the strike angle of 200 degrees. The dip angleis the magnitude of the inclination of the formation from horizontal.The strike angle is the azimuth of the intersection of a plane with ahorizontal surface. Other drilling operating parameters and well boreparameters are also obtained.

For the purposes of calibrating the model and having a baseline forpotential solutions, a drilling simulation using the drillinginformation and the previously used drilling tool assembly is performed.

The offset well information is entered into a simulation program todefine the environment for the drilling simulation. The well bore ismodeled in increments by inputting well survey data from the offsetwell, as shown in FIG. 13. The well survey data is entered to 4,400feet. A 3-D graphical visualization of the modeled well bore is shown inFIG. 14. A scale 570 is used to quantify the dogleg severity of the wellbore 571. Based on the known drilling information, anisotropy indexesare calculated for the formation for use in the drilling simulation.

The drilling tool assembly that was previously used by the drillingoperator is also modeled. The input screen for the previously useddrilling tool assembly is shown in FIG. 14. After modeling the well boreand drilling tool assembly, a drilling simulation is performed from4,300 feet to 4,400 feet. The data at 4,400 feet is then compared to theactual offset well data to ensure accuracy in the model. FIG. 15 shows atabular output of the well bore geometry from the drilling simulation.The data in FIG. 15 is compared to the previously entered offset welldata in FIG. 13. The drilling simulation matches the offset well data,which indicated that the model is ready to be used for predictivepurposes.

The data from the drilling simulation can then be used to predict thewell bore that would be drilled by the previously used drilling toolassembly using the original drilling operating parameters. A predictionto 5,070 feet is shown in FIG. 16. FIG. 16 graphs depth versusinclination angle. The target is to be less than 5 degrees at 5,000feet. The prediction from the drilling simulation shows that the wellbore would have a 6.7 degree inclination at 5,000 feet, which means thatpotential solutions are needed by the drilling operator to drill thedesired well bore.

The selected drilling performance criterion for the solution is to drilla well bore with an inclination of less than 5 degrees at 5,000 feet.One of ordinary skill in the art would appreciate that many potentialsolutions may exist that would be able to drill the well bore in therequired manner. For simplicity, only two of the potential solutions arediscussed. Potential solution A is to use the original 16 inch drillbit, 45 feet of 9-½ inch drill collar, a 15.75″ stabilizer, and then theoriginal drilling tool assembly from component 6 and above as shown inthe drilling tool assembly layout 504 in FIG. 14. Potential solution Bis the original 16 inch drill bit, 45 feet of 11 inch drill collar, a14.81″ stabilizer, and then the original drilling tool assembly fromcomponent 6 and above as shown in the drilling tool assembly layout 504in FIG. 14. Drilling simulations are performed for each of the potentialsolutions.

After performing the drilling simulations, potential solution A and Bare compared. In this example, plots of depth versus inclination angleare used. Those plots are shown in FIGS. 17A and 17B. FIG. 17A showsthat potential solution A will result in an inclination of 5.4 degreesat 5,000 feet. This is an improvement over the original drilling toolassembly, but still greater than the desired inclination. FIG. 17B showsthat potential solution B will achieve an inclination of 4.1 degrees at5,000 feet. Potential solution B is the selected solution for thedrilling operator.

While only two potential solutions were used in the above example, oneof ordinary skill that additional potential solutions may be simulated.For example, different drill bits may have been potential solutions tothe inclination of the well bore. Also, the drilling operator may havebeen concerned about ROP in addition to the inclination. In that case,additional comparisons of drilling performance criteria betweenpotential solutions to select a solution. The selected solution may notbe the best for ROP or inclination, but instead provide a balance ofthose drilling performance criteria.

Drilling trajectory prediction as described in the preceding example maybe of great value in drilling a well. In one or more embodiments, anaccurate drilling trajectory prediction may be used to reduce oreliminate the need for directional measuring systems during drilling.The requirement for repeated well surveys may also be reduced.

One of ordinary skill in the art will appreciate that a drillingperformance problem may have many potential solutions. A potentialsolution may be adjusting the location of a single component, such as astabilizer, in a drilling tool assembly. A potential solution may be touse a different drill bit with a previously used drilling tool assembly.In some embodiments, a potential solution may be an entirely differentdrilling tool assembly. Alternatively, a potential solution may be toonly adjust drilling operating parameters, such as RPM and WOB, toachieve the desired drilling performance. In other embodiments, apotential solution may be the addition or removal of a component in thedrilling tool assembly. Examples of potential solutions are forillustrative purposes only, and are not intended to limit the scope ofthe invention.

Aspects of embodiments of the invention, such as the collection andevaluation of drilling data and the performance of dynamic simulations,may be implemented on any type of computer regardless of the platformbeing used. For example, as shown in FIG. 18, a networked computersystem (960) that may be used in an embodiment of the invention includesa processor (962), associated memory (964), a storage device (966), andnumerous other elements and functionalities typical of today's computers(not shown). The networked computer (960) may also include input means,such as a keyboard (968) and a mouse (970), and output means, such as amonitor (972). The networked computer system (960) is connected to alocal area network (LAN) or a wide area network (e.g., the Internet)(not shown) via a network interface connection (not shown). Thoseskilled in the art will appreciate that these input and output means maytake other forms. Additionally, the computer system may not be connectedto a network. Further, those skilled in the art will appreciate that oneor more elements of the aforementioned computer (960) may be located ata remote location and connected to the other elements over a network.

Embodiments of the invention may provide one or more of the followingadvantages. Embodiments of the invention may be used to evaluatedrilling information to improve drilling performance in a given drillingoperation. Embodiments of the invention may be used to identifypotential causes of drilling performance problems based on drillinginformation. In some cases, causes of drilling performance problems maybe confirmed performing drilling simulations. Additionally, in one ormore embodiments, potential solutions to improve drilling performancemay be defined, validated through drilling simulations, and selectedbased on one or more selected drilling performance criteria. Further,methods in accordance with one or more embodiments of the presentinvention may provide predictions for the drilling performance of aselected drilling tool assembly.

Further, it should be understood that regardless of the complexity of adrilling tool assembly or the trajectory of the well bore in which it isto be constrained, the invention provides reliable methods that can beused to determine a preferred drilling tool assembly design for drillingin a selected earth formation under defined conditions. The inventionalso facilitates designing a drilling tool assembly having enhanceddrilling performance, and may be used determine optimal drillingoperating parameters for improving the drilling performance of aselected drilling tool assembly.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate hat other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. A method for improving drilling performance of a drilling toolassembly, the method comprising: identifying a drilling performanceparameter to be improved; defining at least one potential solution toimprove the drilling performance parameter; performing a drillingsimulation of the at least one potential solution, wherein the drillingsimulation comprises simulating an effect on the drilling tool assemblyof an interaction of at least one cutting element of a drill bit with anearth formation; and determining, based upon the drilling simulation,whether the drilling performance parameter is improved by the at leastone potential solution.
 2. The method of claim 1, wherein the evaluatingcomprises performing a drilling simulation to simulate an originaldrilling operation.
 3. The method of claim 1, wherein the definingcomprises defining two potential solutions, and wherein the determiningcomprises differentiating between the two potential solutions based upona degree of improvement of the drilling performance parameter.
 4. Themethod of claim 1, further comprising: using a solution selected fromthe at least one potential solution to drill a well.
 5. The method ofclaim 4, further comprising: obtaining post-run drilling informationcollected during the using the solution; and determining a degree towhich the drilling performance parameter has improved.
 6. The method ofclaim 1, wherein the at least one potential solution comprises anadjusted drilling tool assembly design parameter.
 7. The method of claim1, wherein the at least one potential solution comprises an adjusteddrilling operating parameter.
 8. The method of claim 1, furthercomprising: viewing a graphical visualization of the drillingsimulation.
 9. The method of claim 8, wherein the graphicalvisualization comprises a color scheme for the drilling tool assemblyaccording to a drilling performance parameter selected from the groupconsisting of lateral vibration, axial vibration, torsional vibration,force on a component, rate of penetration, torque, weight on bit, andpath of the drill bit.
 10. The method of claim 1, further comprising:outputting a drilling performance parameter selected from the groupconsisting of lateral vibration, axial vibration, torsional vibration,force on a component, rate of penetration, torque, weight on bit, anddirection of path drilled.
 11. The method of claim 10, wherein thedrilling performance parameter is displayed as a graphical visualizationof the drilling tool assembly.
 12. The method of claim 11, wherein thegraphical visualization comprises a color scheme for the drilling toolassembly according to a drilling performance parameter.
 13. The methodof claim 10, wherein the drilling performance parameter is displayed asa plot of the at least one drilling performance parameter with respectto a time.
 14. The method of claim 10, wherein the drilling performanceparameter is displayed as tabular data.
 15. A drilling tool assemblydesigned using the method of claim
 1. 16. A computer system forimproving drilling performance of a drilling tool assembly comprising: aprocessor; a memory; a storage device; and software instructions storedin the memory for enabling the computer system under control of theprocessor, to: identify a drilling performance parameter to be improved;define at least one potential solution to improve the drillingperformance parameter; perform a drilling simulation of the at least onepotential solution, wherein the drilling simulation comprises simulatingan effect on the drilling tool assembly of an interaction of at leastone cutting element of a drill bit with an earth formation; anddetermine, based upon the drilling simulation, whether the drillingperformance parameter is improved by the at least one potentialsolution.
 17. The computer system of claim 16, further comprising thesoftware instructions to: perform a drilling simulation to simulate anoriginal drilling operation.
 18. The computer system of claim 16,further comprising the software instructions to: obtain post-rundrilling information from a using of the at least one potential solutionand determine a degree to which the drilling performance parameter hasimproved.
 19. The computer system of claim 16, wherein the at least onesolution comprises an adjusted tool assembly design parameter.
 20. Thecomputer system of claim 16, wherein the at least one solution comprisesan adjusted drilling operating parameter.
 21. The computer system ofclaim 16, further comprising the software instructions to: output adrilling performance parameter selected from the group consisting oflateral vibration, axial vibration, torsional vibration, force on acomponent, rate of penetration, torque, weight on bit, and direction ofpath drilled.
 22. The computer system of claim 21, wherein the drillingperformance parameter is displayed as a graphical visualization of thedrilling tool assembly drilling the earth formation.
 23. The computersystem of claim 21, wherein the graphical visualization comprises acolor scheme for the drilling tool assembly according to a drillingperformance parameter.
 24. The computer system of claim 21, wherein thedrilling performance parameter is displayed as a plot of the drillingperformance parameter with respect to a time.
 25. The computer system ofclaim 21, wherein the drilling performance parameter is displayed as aset of tabular data.
 26. The computer system of claim 21 furthercomprising: an output means to display the output.
 27. A method forimproving drilling performance of a drilling tool assembly, the methodcomprising: performing a drilling simulation to simulate an originaldrilling operation, wherein the drilling simulation comprises simulatingan effect on the drilling tool assembly of an interaction of at leastone cutting element of a drill bit with an earth formation; anddefining, based upon the drilling simulation, at least one solution toimprove a drilling performance parameter.